1. Field of the Invention
This invention relates to improvements in means for fitting ophthalmic lenses in spectacles frames and has particular reference to a device for locating the optimum position for lens optical centers relative to extreme lateral and inferior edges of the lenses as determined by locations of patient's pupils relative to properly fitted spectacles frames intended to receive the lenses.
2. Description of the Prior Art
The fitting of lenses to various shapes and sizes of frames especially of the rimless type is ordinarily a tedious, time consuming and relatively difficult undertaking requiring special skills. The great number of aids offered in the prior art for allegedly facilitating ophthalmic glazing are evidence of the generally recognized problems involved in obtaining optimum ophthalmic glazing. These glazing aids include for example lens blank and frame coordinating charts of which the disclosure of U.S. Pat. No. 3,740,857 is exemplary; ordinary millimeter scales and/or scales having special nose rests, pointers and auxiliary measuring devices applied thereto as for example in U.S. Pat. No. 1,912,107; and special fitting frames of which those represented in U.S. Pat. Nos. 1,505,447 and 638,727 are exemplary.
While these prior art devices may relieve some of the problems and tediousness in measuring for optical center location and lens fitting in general, the accuracy of fitting therewith continues to rely heavily upon the skill and painstakingness of the practitioner together with similar carefulness in proper interpretation and use of the measuring information in the lens finishing shop since this information is not taken from or applied directly to the ultimate spectacles frame i.e. that selected by the patient.
Prior art approaches to applying measurements directly to patient selected and prefitted frames, have required exceptionally ungainly and overly complicated apparatuses supplying only the heretofore conventional measurements of pupillary distance (PD) from the center of the frame and vertical height of bifocal segment, for example, in each case. Some of the Prior Art additionally require the learning and practice of relatively complicated operating procedures involving in each case an unduly number of sequentially performed steps including, to name a few, those of measuring one lens fitting parameter such as PD, the necessity to thereafter neutralize the instrument components, and subsequently separately individually measuring another parameter such as optical center or reading segment height.
An improvement over the prior art of U.S. Pat. No. 2,491,312 is disclosed in U.S. application Ser. No. 619,083 filed Oct. 2, 1975, now U.S. Pat. No. 4,055,900 in the name of the present inventors. Therein the earlier instrument costliness, ungainliness and tediousness of operation have been largely obviated. This latter invention, however, falls somewhat short of affording maximum simplicity in optical center locating apparatus especially in situations involving optical center location for rimless ophthalmic spectacles frames.
Accordingly, it is an object of the present invention to accomplish greater simplicity and economy of construction with unusual ease and straightforwardness of operation in lens optical center locating procedures and apparatuses; and
Another object is to render the scheme and instrumentation of the invention adaptable to use with patient prefitted rimless or rimmed spectacles and straightforwardly adaptable to the traditional boxing method of lens layout for ophthalmic glazing: those interested in details of this method may refer to "The Boxing Method of Specifying Eye Size" by Glenn A. Fry, Ph.D. Journal of the American Optometric Association, February, 1959, pages 481-484.
Other objects and advantages of the invention will become more readily apparent from the description which follows;